Wireless Communication using the IrDA Standard · PDF file · 2010-01-27Web Seminar January 21, 2004 Wireless Communication using the IrDA ... be giving a brief introduction to wireless

Microchip Technology Inc.Web Seminar January 21, 2004

Wireless Communication using the IrDA® Standard Protocol Page 1

© 2004 Microchip Technology Incorporated. All Rights Reserved. Wireless Communication using the IrDA® Standard Protocol 1

Wireless Communicationusing the

IrDA® Standard Protocol

Thank YouMy name is Mark Palmer and I am the application engineer supportingMicrochip�s family of IrDA Standard Protocol Handling devices. Today we willbe giving a brief introduction to wireless communication using the IrDAStandard protocol.




Agenda� Why use infrared?� Typical applications� An IrDA® Standard system� IrDA protocol stack� Connection sequence� Host UART interface� Complete support� Summary

This agenda gives you an idea of the topics we will cover. First we willdiscuss why use infrared, and what are some of the typical applications. Wewill then give a high level look at an IrDA Standard system. From this systemwe will discuss the IrDA protocol stack, the connection sequence that occurson the IR interface, and then the Host UART interface between the MicrochipProtocol Handler (MCP215x/MCP2140) and the Host Controller. We will thenwrap up with what Microchip offers to support this product family.




Why use Infrared?Wire

ConfigurationRS-232 DB-9Host

Controller

Wire

In a typical embedded application, the interface to the outside world is aserial cable. This embedded application will have the Host controller, an RS-232 line driver, the DB-9 connector, and then the serial cable.Microchip�s Protocol Handler devices allow an analogous visualization:




Why use Infrared?Wire

ConfigurationRS-232 DB-9Host

Controller

Wire

MCP21xx OpticalTransceiver

HostController

LightIrDAConfiguration

Protocol Handler

Here the RS-232 line driver is replaced by the MCP21xx Protocol Handler,The DB-9 connector is replaced by the Optical Transceiver circuitry, and theSerial cable is replaced by light.So what are the advantages of IrDA




Why use Infrared?

� Enhances mobility via easywireless connections

� Eliminates connection cables� Universal standard

� No transmitter interaction/interference

� Safe to use in anyenvironment

� Easy regulatory approval� Low Cost

WireConfiguration

RS-232 DB-9HostController

Wire

MCP21xx OpticalTransceiver

HostController

LightIrDAConfiguration

Protocol Handler

Enhances mobility since cables are no longer required. Think how useful itwould be if to transfer data between PDAs you had to have a cable. Woulddata (address contacts, photos, programs, ..) be transferred as often?Since it is a Universal standard (PDAs, notebook PC, mobile phones, ...),ensures interoperability with many existing devicesSome other wireless technologies (such as RF) radiate noise, they cancause interaction and interference. Since IR uses light, which is directional,these issues don�t occur. This lack of interference means that IR is safe touse in any environment (planes, hospitals, �). This also eases regulatoryapproval.Lastly, the cost of a wireless solution can be implemented near the samecost as a wired solution.




Typical IrDAStandard Applications

IrDA Standard compliant ports are available on:� PDAs� Notebook Computers� Mobile phones� Printers� Pagers� Watches (Heart Rate Monitor)

Some of the common devices where you will find IrDA standard ports are:PDAs, Notebook PC, some printers, Mobile Phones and pagers, and the onethat I use regularly a Heart Rate monitor watch, which I use to log myexercise routines. The IrDA interface is used to download the exercise datato my PC.




An Embedded SystemHost

Controller

TX

RX

UAR

TEncode

Decode

TX TXIR

RX RXIR

MCP215X(Protocol Handler)

UARTControl

RTSCTSDSRDTR

CDRI

OpticalTransceiver

TXD

RXD

Protocol Handler

SecondaryDevice

Host Interface

Primary DeviceDevice (PDA)

with IrDA StandardInfrared Port

Here we have the IrDA Standard system.Starting on the right we have the Primary Device, in this case a PDA.Left of the PDA we have the embedded system, which is the IrDA StandardSecondary Device. This Embedded System can be broken into three parts:1. The IR side, with Optical Transceiver2. The Protocol Handler3. The Host Controller side, includes Host UART




The IrDA Protocol �Stack�

Optional IrDA Data Protocols not

Implemented in the MCP215x and MCP2140

Note 1: The MCP215X and MCP2140 implements the 9-wire �cooked" service class serial replicator

implemented in the MCP215X and MCP2140

2: An Optical Transceiver is required

AsynchronousSerial IR (2, 3, 4) (SIR)(9600 - 115200 Baud)

SynchronousSerial IR(1.15 MBaud)

SynchronousFast IR (FIR)(4 MBaud)

3: MCP2120 only implements the Encoding/Decoding portion of Physical Layer4: MCP2140 operates at a fixed 9600 Baud

So first we look at the Protocol Stack that is implemented in the ProtocolHandler.The IrDA Standard is a network protocol. The IrDA Organization hasremapped the Standard OSI network model into these Protocol layers fortheir documentation purposes.At the bottom of the Stack is the Physical layer. This specifies how the datalooks like (bit format, IR/differential/�.). IrDA has 3 specifications. MostDevices, including PDAs use the Asynchronous Serial IR, or SIR. SIRsupports transmission speed of 115200 Baud. PCs and some printersimplement Synchronous Fast IR, or FIR. FIR supports transmission speed of4 Mbaud, but to ensure backwards compatible with SIR it also startsnegotiation at 9600 Baud (that is why PCs can talk to PDAs).










LM-IAS Tiny Transport Protocol (Tiny TP)

IR Link Management - Mux (IrLMP)

IR Link Access Protocol (IrLAP)AsynchronousSerial IR (2, 3, 4) (SIR)(9600 - 115200 Baud)




Now we move to the middle area of the Protocol Stack.These layers handle the Routing of the Data, Error Correction for the DataPacket, Link Management, other communication issues, as well asstructuring the information for the Application Layer of the Protocol Stack.










IrTRAN-P IrObex IrCOMM (1) IrMC

LM-IAS Tiny Transport Protocol (Tiny TP)

IR Link Management - Mux (IrLMP)

IR Link Access Protocol (IrLAP)AsynchronousSerial IR (2, 3, 4) (SIR)(9600 - 115200 Baud)



IrLAN


Then we add the Application layer. At the Application layer is where thereare different Application Protocols. You can think of these applicationprotocols as languages. If two devices try to communicate, and they are notusing the same protocol (language) then they will not be successful.

When many people think infrared, they think �Beaming�. That is when theyselect an Object to �beam� to another device. This technique actually usesIrObex, which stands for IR Object Exchange. In this case the characteristicsof the �Object� (file, program, photo, �.) are know before the object istransferred.

IrCOMM is the IrDA Standard specification for the replacement of thecommunication ports (Serial and Parallel). The characteristics of theinformation that will be transferred is unknown.

THE MCP215x/MCP2140 HANDLES ALL THIS PROTOCOL, Theapplications Host Controller is only required to send and receive UART dataand follow the Flow Control signals of the Host UART interface.




Connection Sequence

NormalDisconnectMode (NDM)

DiscoveryMode

NormalResponseMode (NRM)

When link is closed(or broken)

If link is closed(or broken)

There are three states that the IrDA Standard protocol stack could be in.These are:* Normal Disconnect Mode (NDM)* Discovery Mode* Normal Response Mode (NRM)NDM is the state where the Primary Device is searching for other IrDAStandard devices (with the same Application Layer Protocol) and theSecondary Device is waiting for interrogation from a Primary DeviceDiscovery is the state where the Primary Device and the Secondary Devicedetermine each others capabilities (and use the Highest commondenominator)NRM is the state where Data and Status information is transferred back andforth. Status information is also the mechanism to verify if a link is stillconnected (not blocked).




Connection Sequence -Normal Disconnect Mode

Primary Device Secondary Device

No Response

Send XID Commands(timeslot n, n+1, �)

XID Response in timeslot y(claiming this timeslot)

No Response to these XIDs

No Response to Broadcast ID

Broadcast ID

Finish sending XIDs(max timeslot - y frames)

Here the Primary Device sends out XID commands. The XID command willindicate a timeslot (typically 0 to 7 - dependant on the IrDA Standard Stackused).When the Secondary Device gets in range of the Primary Device, it willrespond to one of these XID commands - claiming that timeslot. ThisSecondary Device will then ignore the remaining XID commands.The IrDA Standard protocol allows the Primary Device to identify up to 8devices, The MCP215x and MCP2140 devices are designed for point-to-point communication (not multi-point).The Primary Device will then transmit a Broadcast ID which no SecondaryDevice will respond to.




Connection Sequence -Discovery Mode


UA response with parametersusing connect address

Send SNRM Command(w/ parameters andconnection address)

Open channel for IASQueries

Confirm channel open for IAS

Send IAS Queries

Open channel for Data

Provide IAS responses

Confirm channel open for Data

MCP2150 - CD signal is lowMCP2155/MCP2140 - DSR signal is low

Discovery is the state where the Primary Device and the Secondary Devicedetermine each others capabilitiesFirst the Primary Device transmits an SNRM command with parameters andconnection addresses. The Secondary Device will then issue a UA responsewith parameters using the specified connection address.The Primary Device then Opens a channel for IAS Queries, which theSecondary Device will confirm.Now it is time for the capabilities of each device to be determined. Thesecapabilities include: IR Baud Rate, Data Packet Size, Turn Around times,and a few other things. So the Primary Device will send its capabilities, andthe Secondary Device will respond with its capabilities. The Highest commondenominator will then be used to optimize system performance.Now it is the responsibility of the Primary Device to send the Open Channelfor Data. On a PC this will only occur after a PC program has �attached� tothe IR port - such as HyperTerminal. On a PDA this occurs when the 1stbyte (packet) of data is ready to be transferred. The Secondary Device willconfirm that the channel is open for data. When the MCP215x or MCP2140confirm that the channel is open for data, they will also drive the appropriatesignal (CD or DSR) low to indicate that the link is now open, and Data maybe transferred




Connection Sequence -Normal Response Mode


Send Data or Status

Shutdown link

Confirm shutdown(back to NDM state

Send Data or Status

Send Data or Status

Send Data or Status

Confirm channel open for DataMCP2150 - CD signal is lowMCP2155/MCP2140 - DSR signal is low

NRM is the state where Data and Status information is transferred back andforth. Status information is also the mechanism to verify if a link is stillconnected (not blocked).If the link is blocked for longer then the Link timeout, then the devices willreset to the NDM state.Whenever communication is completed, the Primary Device may shut downthe link. The Secondary Device will confirm this command and both deviceswill return to the NDM state.




An Embedded SystemHost

Controller

TX

RX

UAR

TEncode

Decode

TX TXIR

RX RXIR


UARTControl

RTSCTSDSRDTR

CDRI

OpticalTransceiver

TXD

RXD

Protocol Handler

SecondaryDevice

Host Interface

Primary DeviceDevice (PDA)

with IrDA StandardInfrared Port

Now we are going to look at the interface between the Host Controller andthe Protocol Handler, or the Host UART interface.




Host UART HardwareHandshaking - continued

� The CTS and RTS pins are used for thecontrol of the data flow between theMCP215x/MCP2140 and the Host Controller� CTS indicates when the Host Controller may

send data to the Protocol Handler� RTS indicates when the Protocol Handler may

send data to the Host Controller� The MCP215x CTS signal is windowed

� Protocol Handler is either operating on IRinterface or Host UART interface

The CTS signal must be monitored by the Host Controller, so the HostController knows when it can transfer data to the Protocol Handler device.Any data transferred while the CTS signal is high is ignored, and will be�lost�. That is will not be transferred to the Primary Device.Occasionally the Host Controller may be busy and not able to receive thingsfrom the Protocol Handler. For this, the Host Controller can control the stateof the RTS signal. This indicates when the Protocol Handler can transmit thedata it has received from the Primary Device on to the Host Controller. If theRTS signal is de asserted too long, while the Protocol Handler has datapending for the Host Controller, the link will be closed.Now the MCP215x devices window the time between the IR interface andthe Host UART interface. So the CTS signal can only be valid during thewindow where the Protocol Handler is operating on the Host UART




Host UART HardwareHandshaking - continued

� MCP215x� Window is 22ms� Once �Communications� is ok (CTS is Low),

Data can be transmitted for 22ms, or for 64bytes (Host UART Receive Buffer size)Host UARTBaud Rate

11520057600

192009600

Bytes Transfer (in 22 ms)

253 ( > 64 byte limit)126 ( > 64 byte limit)

42 ( < 64 byte limit)21 ( < 64 byte limit)

This Window is 22ms and the MCP215x Host UART Receive Buffer is 64Bytes. So the Host Controller can transfer data for this 22ms up to amaximum of 64 Bytes.So the table shows how many bytes can be transferred in 22ms at a givenbaud rate. Baud rates 19200 Baud and below will not be able to transfer the64 Bytes in the Window time. With a Baud rate 57600 and Greater, the 64Byte limit can be reached




MCP215x CTSHardware Handshaking

CTS

Receive Buffer Empty, MCP215x can Receive Data

Receive Buffer has received 60 bytes (Baud Rate ≥ 57600), CTS pin is driven high, Receive Data Time Window still open

Receive Data Time Window (22ms)

Receive Data Time Window closed,MCP215x will transmit data later. Data will be processed and formatted

Here is a visualization of the CTS and Receive Data Time Windowoperation.Assuming that the Host controller Baud rate is 57600, that there is no Byte toByte spacing, and minimal latency when CTS goes low to Data to starttransfer.When CTS goes low, the MCP215x Host UART Receive Buffer is empty.Once 60 Bytes have been received, the CTS signal will be driven high. Thisis done to indicate to Host Controllers that use a transmit FIFO on theUART. The MCP215x can receive an additional 4 bytes. When 64 bytes arereceived, the Data will be processed, formatted, and then transmitted to thePrimary Device.If the Host UART Baud rate is 19200, then the Receive Data Time windowwill close, which forces CTS High, before 64 Bytes could be received. TheData in the Host UART Receive Buffer will be processed, formatted, andthen transmitted to the Primary Device.Any data that is being received when CTS is driven high will not be lost.




MCP2140 CTSHardware Handshaking

CTS


Receive Buffer has received 23 bytes,CTS pin is driven high, Receive Buffer may still receive 6 bytes

Receive Buffer Full (29 Bytes),MCP2140 will transmit data later. Data will be processed and formatted


For the MCP2140, there is no Receive Data Time Window. CTS is low whenthe Host UART Receive Buffer has space available.When CTS falls, the entire 29 Bytes of the Host UART Receive Buffer areavailable. CTS will be driven high when 23 bytes are in the Host UARTReceive Buffer. Again this is to �give notice� to Host Controllers that use atransmit FIFO on the UART.




Complete Support SolutionHost

Controller

TX

RX

UAR

TEncode

Decode

TX TXIR

RX RXIR


UARTControl

RTSCTSDSRDTR

CDRI

OpticalTransceiver

TXD

RXD

Protocol Handler

SecondaryDevice

Host Interface

Primary Devicewith IrDAStandardInfrared Port(PDAs,NotebookPC, �)

App Notes Available:� Programming the Palm® OS(AN888)� Discrete Transceiver design (AN243)

In Development:� Programming Pocket PC� Programming Windows® XP

This visual shows where Application Notes are done to assist the customerin the development of their system.

We have:1 Ap Note on the interface between the MCP215x and a Host Controller1 Ap Note for the Fundamentals of Optical Transceivers1 Ap Note on Programming Primary Device

Programming the Palm OS for Embedded IR Applications

In Development are:2 Ap Notes on Programming Primary Device

Programming the PocketPC OS for Embedded IRApplicationsProgramming the Windows XP OS for Embedded IRApplications




Summary

� Microchip�s family of IrDA® StandardProtocol Handles enables wirelessconnectivity to easily be added to embeddedapplications.

� This universal interface allows commonlyavailable low cost devices, such as PDAs, tointerface to the embedded system.

Microchip�s IrDA Standard Protocol Handler devices can easily be added tosystems currently using a serial connection with flow control. This whenallows these embedded systems to interface to the many existing deviceswith an IrDA port.List of some of the available Application Notes, Data Sheets, and otherreference material is available on the next couple of slides. For a completelist of Information Please visit the Infrared Communication Design page ofthe Microchip Web Site.




Documentation Support� Data sheets:

� MCP2150 Data Sheet - DS21655A� MCP2155 Data Sheet - DS21690A� MCP2140 Data Sheet - DS21790A� MCP2120 Data Sheet - DS21618A

� Application Notes:� AN858 - Interfacing the MCP215x to a Host Controller� AN888 - Programming the Palm OS® for Embedded IR Applications� AN243 - Fundamentals of the Infrared Physical Layer� AN758 - Using the MCP2150 to add IrDA Standard Wireless Connectivity� AN756 - Using the MCP2120 for Infrared Communication

Here is a list of documentation that is available from our website including anumber of application notes.




Other Reference Material

� Microchip Infrared Connectivity InternetDesign Center� www.microchip.com/infrared

� IrDA Standards download pagehttp:/www.irda.org/standards/specifications

� Microsoft documentation http:/www.microsoft.com/hwdev/infrared

In addition there are a number of web sites that offer additional informationon wireless communication using the IrDA Standard.




The Microchip name and logo, the Microchip logo, are registered trademarks of Microchip Technology Incorporated in the U.S.A. and other countries.PICDEM is a trademark of Microchip Technology Incorporated in the U.S.A. and other countries.

IrDA is a registered trademark of the Infrared Data Association

All other trademarks mentioned herein are property of their respective companies.

All rights reserved. Copyright © 2003 Microchip Technology Incorporated.Information contained in this publication regarding device applications and the like is intended through suggestion only and may be superseded by updates. Norepresentation or warranty is given and no liability is assumed by Microchip Technology Incorporated with respect to the accuracy or use of such information, orinfringement of patents or other intellectual property rights arising from such use or otherwise. Use of Microchip�s products as critical components in life support systemsis not authorized except with express written approval by Microchip. No licenses are conveyed, implicitly or otherwise, under any intellectual property rights.

Documents

Wireless Communication using the IrDA Standard · PDF file · 2010-01-27Web Seminar January 21, 2004 Wireless Communication using the IrDA ... be giving a brief introduction to wireless